Dyeing of polyester fibers with acid leuco vat dyes



iatented Feb. 3, 1953 DYEING OF POLYESTER FIBERS WITH ACID LEUCO VAT DYES- Hans Luttringhaus, Ghatham, Henry R. Mautner, Clifiside Park, N. J., and Alex A. Arcus, Bellerose, N. Y.

No Drawing. Application March 14, 1951,

Serial No. 215,624

7 Claims.

This invention relates to a process for dyeing linear polyester fiber, particularly of linear condensation polymers of terephthalic acid and a polymethylene glycol, especially ethylene glycol (commonly known as Fiber V), with vat dyestuffs.

Polyester fibers of the aforesaid type, such as Fiber V, have very poor aflinity for dyestufis. The best colorations thus far produced thereon have been with aqueous dispersions of Waterinsoluble dyestuffs having afiinity for cellulose acetate. However, these dyestuffs produce only light or medium shades of poor fastness properties, especially in their resistance to light and washing.

It has also been proposed to pad dispersions of pigment dyestuffs on Fiber V, followed by heat treatment, e. g. by immersion of the padded material in molten metal for a short period of time at temperatures of the order of 400 While an improvement in fastness is obtained by this treatment, the depth of shade produced remains seriously limited for most dyestuffs, so that no adequate range of shades can be obtained. Vat dyestuiis, when applied in the form of an aqueous alkaline vat, fail to exhaust satisfactorily on Fiber V.

It is an object of this invention to produce colorations with vat dyestufis on Fiber V and similar polyester fibers in a full range from light to dark shades, having excellent i-astness to light and Washing.

We have discovered that polyester fibers such as Fiber V can be dyed with vat dyestuffs in dark as well as medium and light shades by impregnating (e. g. padding) the fiber or textile material with an acidified vat (i. e., an acid-reacting aqueous colloidal dispersion of the leuco compound of a vat dyestuff, as produced, iorexample, by acidifying an aqueous alkaline vat as ordinarily applied for producing vat colorations on cellulosic fibers and containing a dispersing agent sired depth, having excellent fastness to light and Washing.

The heat treatment of the textile material padded with an acid leuco vat dye dispersion in accordance with this invention can be carried out by radiation (e. g. by exposing the material to infrared rays), by convection (e. g. by exposure of the material to circulating hot air or other gases), or by conduction (e. g. by passage over a heated surface or immersion in a heated water-immiscible liquid). Advantageously, the material is subjected to heat treatment in a curing range employing infrared rays, circulating hot gases, or heated rollers, or by temporarily immersing the material in, or passing it through a molten metal bath maintained at the desired temperature. The padding operation and heat treatment can be conveniently carried out in a continuous manner on piece goods, warps, slubbing and the like, by progressively passing such material through padding equipment and a heating zone or apparatus.

The material can be predried after the padding operation and before the heat treatment, or drying can be efiected in the course of the heat treatment. The effective heating period at the temperature range specified above is generally limited to that portion of the heating after evaporation of moisture carried by the material.

Vat dyes of the quinonoid or indigoid series can be used in the process of this invention. Acid aqueous dispersions of the corresponding leuco compounds as employed for paddin the polyester fiber in accordance with the invention are prepared by vatting the dyestuff in an aqueous alkaline solution with an alkali metal hydrosulfite or equivalent reducing agent, incorporating therein a dispersing agent effective in acid solution, and acidifying the resulting alkaline vat to adjust the pH to the range of .2 to 5. Suitable dispersing agents are, especially, surface-active water-soluble sulfonic acids such as alkyl aryl sulfonates, e. g. higher alkyl benzene sulfonates, sulfonated condensation products of naphthalene and formaldehyde or their homologs, isopropyland isobutyl-naphthalene sulfonates, and aliimmersion in, or passage through, a molten metal bath, metals or alloys suitable for use are those melting substantially below the temperature of the heat treatment, and particularly below the boiling point of water. The latter metals and alloys can be used without difficulty from local solidification of the metal, not only in the treatment of predried materials but also with moist padded materials. A suitable alloy for this purpose is Wood,s metal, composed of 50% bismuth, 25% lead, and 12.5% each of tin and cadmium. Other bismuth-lead alloys containing tin and/or cadmium are also known having melting points.

10 parts of Indan-threne Brilliant Pink E Paste (Colour Index No. 1210) were vatted with 2.5 parts of caustic soda and 2.75 parts of sodium hydrosulfite in about 200 parts of water, having dissolved therein 3 parts of a higher alkyl benzene sodium sulfonate dispersing agent. 16.6 parts of aqueous 28% acetic acid were added to acidify the vat. The mixture was then diluted with water to a volume equal to that of 250 parts of water. Fiber-V piece goods were padded with the resulting leuco vat dye dispersion at 180 F., and dried. The material was then heated I) in a curing range at 350 F. for minutes, and then scoured in an aqueous detergent solution, oxidation of the dyestufi to develop its coloration being efiected by atmospheric oxygen. A brilliant red shade was produced having excellent fastness to light and washing.

Example 2 parts of Indanthrene Brilliant Pink R Paste, employed in Example 1, were vatted with 1.7 parts of caustic soda and 2 parts of sodium hydrosulfite in about 50 parts of water containing 1 part of a sulfonated formaldehyde-naphthalene condensation product as a dispersing agent. 11.4 parts of 28% acetic acid, diluted with 50 parts of water were added to acidify the vat, and suflicient water was added to adjust the volume of the resulting dispersion to that of 150 parts of water. Fiber V slubbing was padded with the resulting aqueous leuco vat dyestuii dispersion at 180 F., the material retaining about 100% of its weight of the padding liquor. The material was then passed, while wet, through a Woods metal bath maintained at 350 l t, the duration of the immersion in the metal bath being 2 minutes. As the material emerged from the bath, steam escaped, the fiber being left practically dry. The vat dye coloration was developed by passage through a 1% aqueous solution of potassium persulfate. A brilliant dark red shade was obtained having excellent fastness to light and washing, the coloration being much brighter than that produced with the same dyestuff on cotton or wool.

Example 3 10 parts of Indanthrene Brilliant Violet RR Paste (Colour Index No. 1104) were vatted with 2.5 parts of caustic sod-a and 2.5 parts of sodium hydrosulfite in about 200' parts of water containing 5 parts of the sulfonated formaldehydenaphthalene condensation product of the preceding example. The alkaline vat was acidified by adding 16.6 parts of 28% acetic acid, and the resulting liquor was diluted with water to increase its volume to that of 250 parts of water. Fiber V piece goods was padded with resulting liquor at 180 F. and then dried. The padded material was heat treated in a curing range for a period of 5 minutes at 350 F., and then scoured in an aqueous detergent solution, oxidation being cheated by atmospheric oxygen. A brilliant violet coloration was produced having excellent fastness properties. as obta ned in the preceding examples.

Example 4 5 parts of indigo were pasted with 2 parts of sulfonated castor oil, and vatted with 5 parts of caustic soda and 7.5 parts of sodium hydrosulfite in the presence of 1 part of sulfonated naphthalene-formaldehyde condensation product in about 50 parts of water, and the resulting acid vat was diluted with sur'ficient water to render its volume equal to that of parts of water. Fiber V piece goods was padded with the resulting acid vat, and then passed, while wet, through a Woods metal bath maintained at 350 F., duration of immersion in this bath being 2 minutes. Upon oxidation in an aqueous oxidizing bath as hereinbefore described, a deep navy blue shade of unusual brilliance was obtained, having excellent fastness properties and a much brighter color than shades produced with indigo on wool or cotton.

Example 5 4 parts of Indanthrene Brown It (Colour Index No. 1151) were vatted with 2.3 parts of caustic soda and 2.5 parts of sodium hydrosulfite in about 50 parts of water containing 1 part of sulfonated naphthalene-formaldehyde condensation product. The solution was acidified by adding 15.5 parts of 28 acetic acid diluted with about 50 parts of water, and the volume of the resulting acidified vat was adjusted by dilution with water to a volume equivalent to that of 150 parts of water. Fiber V material was padded with the resulting acid bath and passed, while wet, through molten Woods metal maintained at 350 F., the duration of immersion in the metal bath being 2 minutes. Upon subsequent oxidation in an aqueous persulfate bath, the material was dyed a deep brown shade of excellent fastness to light and wet processing.

Example 6 10 parts of Indanthrene Brilliant Green 3 Double Paste (Colour Index No. 1101) were vatted with 2.5 parts of caustic soda and 2.5 parts of sodium hydrosuifite in about 200 parts of water containing dissolved therein 5 parts of sulionated formaldehyde-naphthalene condensation product. The solution acidified by adding 16.6 parts of 26% acetic acid, and diluted with water suflicient to render the volume equal to that of 250' parts of water. Fiber V material was padded with the resulting acid vat, and after drying, was passed through a curing range in which it was heated at 355 for 5 minutes. After scouring with an aqueous detergent bath, a full bright green shade was produced having excellent fastness to washing and light.

Instead of the vat dyes employed in the examples, which are representative of those of the indigoid, thioindigoid, anthraquinone, and higher polycyclic quinone vat series, other vat dyestuffs of this and related classes can be applied in a similar manner. The vat dyestufis are advantageously vatted in aqueous alkaline solution by treatment with an alkaline metal hydrosulfite or with other reducing agents heretofore employed for preparing alkaline vats. A dispersing agent which is active in acid solution, e. g. of the type employed in the examples, or other surface-active sulfonic acids, is added to the alkaline vat to preserve dispersion of the free vat dyestufl leuco compound which is formed upon acidification. Acidification is accomplished by adding an acid, as described above, so as to adjust the pH to 2 to 5.

The resulting acid vat is advantageously padded on the material, especially at temperatures from 100 to 200 F., the amount of padding liquor retained by the goods being of the same order as the weight of the fabric. As indicated above, the padded material can be dried before heat treatment or in the course of heat treatment. The heat treatment of the invention involves heating the material at from 300 to 400 F. and maintaining it at this temperature for 25 seconds to 5 minutes, especially in a curing range or a molten metal bath.

Development of the coloration by oxidation can be effected by atmospheric oxygen, e. g. in the course of an aqueous scouring operation following the aforesaid heating treatment, or by passing the material through an oxidizing bath such as aqueous hydrogen peroxide, alkali metal persulfates, bichromates and similar compounds. The colorations produced are generally brighter than those produced with the same dye on cotton or wool, and can be made of an desired depth of shade. The fastness of the resulting coloration to light and washing is excellent, even in the case of deep shades.

The polyester fibers which are dyed with vat dyestuffs in accordance with this invention are linear condensation superpolymers of terephthalic acid (or an ester-forming functional derivative thereof) with a polymethylene glycol (preferably, ethylene glycol) having up to methylene groups in a chain interconnecting a pair of terminal hydroxy groups. The fiber is produced by forming the polyester into filaments and stretching, whereby axial molecular orientation occurs, as indicated by production of Well defined X-ray fiber diagrams. The resulting fiber is strong, flexible, and of high melting point and low solubility in water and most organic solvents.

Variations and modifications, which will be obvious to those skilled in the art, can be made in the procedure hereinbefore described without departing from the scope or spirit of the invention.

We claim:

1. A process for dyeing synthetic linear polyester fiber material, which comprises impregnating said material with an acid-reacting aqueous dispersion of the leuco compound of a vat dye, and heating the impregnated material at a temperature of 300 to 400 F. for a period ranging from 25 seconds to 5 minutes, prior to development of the coloration by oxidation of the leuco compound on the fiber.

2. A process for dyeing synthetic linear polyester fiber material, which comprises padding said material with an aqueous dispersion of the leuco compound of a vat dye having a pH of 2 to 5, at a temperature of to 200 F., and heating the impregnated fiber at a temperature from 300 to 400 F. for a period ranging from 25 seconds to 5 minutes, prior to development of the coloration by oxidation of the leuco compound on the fiber.

3. A process as defined in claim 2, wherein the padded material is dried, prior to the heat treatment at temperatures from 300 to 400 F.

4. A process as defined in claim 2, wherein the heat treatment is efiected by immersing the material in a molten metal bath maintained at a temperature from 300 to 400 F., the duration of the immersion ranging from 25 seconds to 5 minutes.

5. A process as defined in claim 2, wherein the aqueous dispersion of the vat dye leuco compound is prepared by acidifying an aqueous alkaline vat of the vat dyestuff, containing an organic sulfonate dispersing agent, with an organic acid in sufiicient amount to yield a pH of 2 to 5.

6. A process as defined in claim 2, wherein the material is progressively padded with the aqueous acidic leuco vat dye dispersion, and progressively exposed to a heating medium, the duration of said exposure being such as to maintain the temperature of the material at 300 to 400 F. for 25 seconds to 5 minutes.

7. A process for dyeing textile fiber of a polyester of terephthalic acid and ethylene glycol with a vat dyestufi, which comprises padding said textile fiber with an aqueous dispersion of a vat dye leuco compound, obtained by acidifying an aqueous alkaline vat of the vat dye containing an organic sulfonate dispersing agent to a pH of 2 to 5, exposing the padded material to a heating medium so as to maintain the temperature of the material at 300 to 400 F. for a period of 25 seconds to 5 minutes, and exposing the heat treated material to an oxidizing agent to convert the vat dye leuco compound to the corresponding vat dye on the fiber.

HANS LUTTRINGlHAUS. HENRY R. MAUTNER. ALEX A. ARCUS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,900,172 Ellis Mar. 7, 1933 2,107,526 Dreyfus Feb. s, 1938 FOREIGN PATENTS Number Country Date 620,584 Great Britain Mar. 28, 1949 OTHER REFERENCES Technical Bulletin (DuPont) for June 1949, volume 5, number 2, pages 82 to 88. 

1. A PROCESS FOR DYEING SYNTHETIC LINEAR POLYESTER FIBER MATERIAL, WHICH COMPRISES IMPREGNATING SAID MATERIAL WITH AN ACID-REACTING AQUEOUS DISPERSION OF THE LEUCO COMPOUND OF A VAT DYE, AND HEATING THE IMPREGNATED MATERIAL AT A TEMPERATURE OF 300 TO 400* F. FOR A PERIOD RANGING FROM 25 SECONDS TO 5 MINUTES, PRIOR TO DEVELOPMENT OF THE COLORATION BY OXIDATION OF THE LEUCO COMPOUND ON THE FIBER. 